1) Field of the Invention
The present invention relates to an entrance structure for introducing a continuous form paper from a paper feeder into a printer.
2) Description of the Related Art
In general, a serial printer such as a wire dot printer is provided with a paper feeder such as a pin-belt tractor for feeding a continuous form paper to a printing location defined by a platen and a printing head. The pin-belt tractor is disposed at an opening area formed in a housing of the printer to be accessed by an operator, whereby a continuous form paper can be set in the pin-belt tractor. In particular, the pin-belt tractor includes a pair of pin-belt assemblies which are engaged with two rows perforations formed along the side margins of the continuous form paper, respectively, and which are supported by the printer frame to be movable toward and apart from each other, so that respective continuous form papers having various widths can be set in the pin-belt tractor.
Recently, many printers are designed so that an automatic loading of the continuous form paper can be carried out. Namely, when a loading switch of the printer is turned ON, the pin-belt tractor is provisionally driven so that the continuous form paper is automatically moved to the printing location, whereby the continuous form paper is made ready for printing. During the automatic movement of the continuous form paper to the printing location, the continuous form paper is first introduced into an interior of the printer housing through an entrance opening formed therein, and then is guided to the printing location along a guide path extended from the entrance theretoward.
The setting of the continuous form paper in the pin-belt tractor is carried out in such a manner that it is tightened between the pin-belt assemblies thereof. Nevertheless, a leading edge portion of the continuous form paper may be misaligned because a width thereof is made greater due to a rise in an air moisture content. In this case, the misaligned leading edge portion of the continuous form paper may be jammed against an upper edge of the entrance opening, resulting in a jam of the continuous form paper thereat. For this reason, the entrance opening is conventionally defined by a sloped guide surface formed on a guide surface forming member. In particular, the guide surface forming member, which may form a part of the printer housing, is disposed above a front end of the pin-belt tractor and has an angle of elevation with respect to the pin-belt tractor. This sloped guide surface enables the smooth passage of the misaligned leading edge portion of the continuous form paper through the entrance opening.
Nevertheless, to ensure a smooth passage of the misaligned leading edge portion of the continuous form paper, the angle of elevation of the sloped guide surface must be as gradual as possible, and in general, is from about 20 to about 30 degrees. Also, to prevent a jamming of a top of the misaligned leading edge portion against an outside edge boundary of the sloped guide surface, a distance between the outside edge of the sloped guide surface and a plane of the continuous form paper must be as high as possible. Before these requirements can be met, the printer housing must be extended at a rear side thereof at which the pin-belt tractor is disposed, resulting in an undesirable bulkiness of the printer housing.